This application claims priority to U.S. Provisional App. Ser. No. 60/474,972 filed Jun. 2, 2003, the contents of which are hereby incorporated by reference. The present invention relates to heat-sealing devices and, more particularly, to tray heat sealers having a press with a heated platen and a shuttle for supporting product.
Heat sealers are known in the art. A specific example of a heat sealer that may be used according to the present invention is the medical tray heat sealer manufactured by Atlas Vac, a division of Planet Products Corp. of Cincinnati, Ohio. The AV model 15:18 heat sealer, manufactured by Atlas Vac, is typical of many heat sealers of this type.
Heat sealers are used to seal packages by simultaneously applying heat and high pressure. Heat sealers typically include a support assembly and a press plate having a heated platen. A product may be placed onto the support assembly and the press plate may advance towards the product such that the heated platen contacts the product and simultaneously applies heat and pressure to seal the product. The amount of pressure being applied and the temperature of the platen must be carefully controlled to ensure a quality seal. However, prior art heat sealers monitor the temperature of the platen using thermocouples embedded in the heater and/or platen and therefore do not accurately measure the temperature of the sealing surface of the platen. In addition, such prior art heat sealers do not contain means for accurately measuring the force of the press plate. Rather, prior art devices typically measure the air or fluid pressure of the cylinder driving the press plate, which is an approximation of the force at best. Also, prior art heat sealers require manual control of the force of the press plate and the temperature of the platen.
Accordingly, there is a need for a heat sealer capable of accurately sensing the temperature of the sealing surface of the platen. Furthermore, there is a need for a heat sealer capable of accurately sensing the direct force exerted by the press plate onto the support assembly and there is a need for a heat sealer that is capable of controlling the operation of the heat sealer, including the sealing temperature and pressure, by a programmable logic controller.